1. Field of the Invention
The present invention concerns an arrangement for a printing mail processing apparatus according that increases the throughput of mailpieces. The invention can be used in franking machines and in similar printing, accounting or mail processing apparatuses.
2. Description of the Prior Art
U.S. Pat. No. 4,746,234 And East German Patent 233 101 B5 disclose a thermotransfer franking machine having a mailpiece transport path with a start sensor that detects the leading edge of a mailpiece, i.e., the start of a letter envelope, and which is connected with a microprocessor in order to start a printing procedure as soon as a mailpiece arrives in the printing station. A thermotransfer printhead is equipped with a shift register, a memory latch unit and driver unit as well as with a series of thermoprinting heating elements disposed orthogonal to the mailpiece transport direction. The thermotransfer printhead is connected with the serial data output of the microprocessor via a register. The microprocessor controller can advance the ink ribbon corresponding to the transport speed mailpieces by means of signals from an encoder.
U.S. Pat. Nos. 4,767,228, and 4,886,384 and European Application 189 984 disclose an ink ribbon cassette for thermotransfer franking machines with a window for the application of a friction wheel to the ink ribbon and a mailpiece transport device as is used in similar form in modern thermotransfer franking machines of the type T1000 and Optimal® of Francotyp-Postalia. When a flap for the cassette bay is opened, a simple mechanism is actuated and the friction wheel is moved away from the ink ribbon of the cassette, allowing the cassette to be removed.
U.S. Pat. No. 5,710,721 and European Application 716 398 disclose an internal franking machine circuit connected with a first microprocessor controller circuit that is the same for all franking machines. The internal franking machine circuit allows the connection of a variable number of sensors and actuators corresponding in type and number to the franking machine type. An adaptation to different printing methods is enabled by the use of different application-specific circuits (ASICs). Production piece numbers for franking machines of the same type, however, in order to justify the cost of the mask programming of the ASICs.
In thermotransfer franking machines of the type T1000 and Optimal®, an encoder disc is fastened on the same axle as a friction wheel and is consequently likewise rotated corresponding to the rotation of the encoder wheel when the ink ribbon is advanced. The operation of the machine is interrupted if an ink ribbon transport does not occur or after the passage of a predetermined time after a franking. This is also called the ejection phase. Up to 25 mailpieces with a maximum thickness of 5 mm can be franked per minute. When the franking event has ended, the microprocessor of the franking machine can check, by means of the start sensor whether the mailpiece (for example the letter envelope) has been transported into the printing region. The start sensor is positioned on the leading edge of the transport path, and the microprocessor thus can detect whether the letter envelope is still lying on the leading edge. It can occur that, due to rotation of the letter envelope, during the franking the letter envelope no longer actuates the start sensor, so the letter envelope is no longer detected during and after the franking. The microprocessor thus can no longer definitely detect with the start sensor whether the letter envelope has already exited the franking machine. If the ejection event were ended due to the interrogation of this start sensor, the letter envelope could remain in the franking machine or could repeatedly trigger the start sensor if it executes an unusual movement, for example with the trailing edge of the letter envelope. This has conventionally been addressed by an (in principle) long ejection phase (without interrogation of the start sensor), but this leads to a lower mailpiece throughput of the franking machine.
The use of additional sensors in order to increase the throughput of mailpieces is known from United States Patent Application Publication No. 2004/0021755, in which mailpieces are transported faster before and after the printing.